In a one-to-N communication system where a base station transmits respective different information to a plurality of (N) mobile stations such as a radio communication service system, the base station is provided with a plurality of antennas, and concurrently transmits different information to a plurality of mobile stations with respective antennas.
In this case, a conventional base station apparatus transmits only one kind of information using one antenna. FIG. 1 is a diagram illustrating a situation where data is transmitted from a plurality of antennas provided in the conventional base station apparatus.
As illustrated in FIG. 1, the base station apparatus is provided with a plurality of antennas (herein, the number of antennas is assumed to be “4”) The base station apparatus concurrently transmits transmission data A at a carrier frequency fA from an antenna A, transmission data B at a carrier frequency fB from an antenna B, transmission data C at a carrier frequency fC from an antenna C, and transmission data D at a carrier frequency fD from an antenna D.
However, there is a problem that the conventional base station apparatus does not provide the effect of the diversity in the case where the number of antennas of a mobile station on a receiving side is “1”. That is, if the number of antennas of a mobile station is a plural number, the diversity effect can be obtained by the space diversity. However, the number of antennas of a mobile station is generally “1”, and in this case, the diversity effect cannot be obtained. In particular, when the fading rate is low, an interval where a received level falls down lasts a long time, and therefore the diversity effect cannot be obtained.